1. Field of the Invention
This invention relates to paperboard containers and more particularly to tapered paperboard containers, examples of which are disposable containers for storage and distribution of solid or liquid food products.
2. Description of the Prior Art
Tapered disposable paperboard containers are widely used in the food industry to package beverages and solid food. Containers are formed from blanks cut from large paperboard sheets. Tapered containers which have been sealed at the side seam and bottom seams are typically stacked for storage, shipment and dispensing prior to filling and sealing.
The paperboard from which the containers are constructed is often coated with a layer of thermoplastic material such as polyethelene on the surface of the carton blank which forms the inside of the container. In areas where the paperboard is overlapped to form a seam, typically both the surfaces in contact are coated with the thermoplastic material to facilitate sealing. Frequently the entire area of both the inner surface and the outer surface are coated with thermoplastic material.
Containers made of coated or uncoated paperboard, when stacked, become difficult to pull apart as a result of successive pressures applied during stacking, the cumulative weight of stacked containers, and friction between the outer surface of a next upper container and the inner surface of a next lower container in a stack. Local atmospheric variables such as temperature and humidity also affect the tendency of stacked tapered containers to resist destacking.
In the past this difficulty of destacking tapered paperboard containers was somewhat overcome by forming tapered containers with a horizontally protruding convexity at one of the upper carton surfaces. The convexity provided a resting ledge between cartons to receive the weight and pressure of stacked cartons independent of the carton wall surfaces. The convexity further provided a graspable protrusion for lifting the cartons away from the cartons of the stack. Such a convexity is disclosed in Gordon, U.S. Pat. No. 4,498,585. In comparison to a conventional tapered carton formed from a conventional carton blank, formation and use of the convexity described in Gordon poses several problems. First, the manufacture of these destackable tapered cartons from flat carton blanks requires a time-consuming and relatively complex step of creating the convexity by forming at least two seals which are not formed in a conventional carton. Second, the convexity necessitates use of a carton blank having at least one flap in addition to the flaps of a conventional carton blank. These differences between the conventional tapered carton and the carton having a destacking convexity require use of modified assembly equipment and performance of several additional assembly steps rendering the formation of such cartons more expensive and time consuming than formation of conventional cartons. Also, the convexity made of paperboard is subject to flatening during handling and stacking such that it becomes deformed, non-protruding and non-functional, causing the stacked cartons to adhere even more tightly due to the added horizontal pressure created by the additional thickness of the deformed convexity between stacked cartons. Moreover, the presence of the convexity impedes the final top closing of the carton because a closure flap must fold over and crush the convexity during closing.
The present invention overcomes the disadvantages of the prior art and obviates the difficulties, extra time and expense of the convexity destacking feature by providing a novel, tapered carton blank uniquely scored and cut, and a novel method of folding and sealing the carton blank to form a carton having a novel destacking feature which does not require additional flaps or additional paperboard, does not require additional sealing steps, is resistant to deformation, and does not impede the final closing of the carton.